1. Field of the Invention
The present invention relates to an ink tank used for a liquid discharge recording apparatus for obtaining recorded images by discharging ink to the recording surface of a recording medium. The invention also relates to a liquid discharge recording apparatus provided with such ink tank. More particularly, the invention relates to an ink tank for ink jet use in the ink jet recording field, and to a printing apparatus provided with such ink tank as well.
2. Related Background Art
Conventionally, in the field of an ink jet recording apparatus, there has been proposed for an ink discharge head an ink tank that exerts negative pressure therein. As one of the easiest methods for generating negative pressure, there is a method to utilize the capillary force of a porous member. The ink tank that uses a method of the kind comprises a porous member, such as sponge, preferably compressed to be housed entirely inside an ink tank for the purpose of retaining ink; and an atmospheric communication port capable of inducing the air into the ink containing portion in order to smooth the ink supply during printing operation.
Here, however, the lower efficiency of ink storage per unit volume may be encountered as a problem when the porous material is used as an ink retaining member.
As the structures of ink tank that may be able to solve a problem of the kind, those shown in FIG. 12 and FIG. 13 are known.
FIG. 12 is a cross-sectional view which shows the structure of a first conventional example. As shown in FIG. 12, the first conventional example is divided into a first containing chamber 51 and a second containing chamber 50. Between the first containing chamber 51 and the second containing chamber 50, an opening portion 63 is arranged. With this opening portion 63, the first containing chamber 51 and second containing chamber 50 are communicated.
For the first containing chamber 51, a porous member formed by urethane sponge or the like is housed as the negative pressure generating member 56. The negative generating member 56 is kept in a state where ink has been absorbed, and the ink-filling portion 58 on the lower part of the negative generating member 56 is filled in with ink. In the negative pressure generating member 56, there is formed ink passage (hereinafter referred to as ink path) through which ink is supplied to the recording head 61. Also, for the second containing chamber 50, ink 53 is retained.
On the lower part of the negative generating member 56, a compressed contact member 59, which is formed by fibers solidified by heat or the like, is inserted, and the ink supply tube 62 through which ink is supplied to a recording head 61 is pressurized to be in contact with the compressed contact member 59 by way of a filer 60.
On the upper part of the first containing chamber 51, the atmospheric hole 55 is arranged through which the air outside 55A flows into the second containing chamber 50. Also, on the side wall that separates the first containing chamber 51 and second containing chamber 50, an atmospheric induction groove 62 is arranged to enable the air outside 55A entering from the atmospheric communication hole 55 to flow into the second containing chamber 50 as a bubble 54.
Now, hereunder, with reference to FIG. 12, the operation of the conventional example will be described.
When a printing apparatus begins its printing operation, the ink which has been absorbed into the negative pressure generating member 56 is consumed at first. Thus, the ink boundary face 57 of the first containing chamber 51 is lowered. As ink consumption advances so that the height of the ink boundary face 57 of the first containing chamber 51 is made from a level at A to a level at B in FIG. 12 to reach the upper edge of the atmospheric induction groove 62, the air outside 55A which has entered by way of the atmospheric communication hole 55 is induced into the second containing chamber 50 as a bubble 54 through the negative pressure generating member 56 and the atmospheric induction groove 62. When a bubble 54 enter the second containing chamber 50, the amount of air in the second containing chamber 50 becomes greater to press the ink boundary face 52 of the second containing chamber 50 downward.
Thus, the portion of ink which has been pressed downward is allowed to flow into the first containing chamber 51 through the opening portion 63. The ink 53 that has flown into the first containing chamber 51 is once absorbed into the negative pressure generating member 56. Then, through the ink path thereof (not shown) ink is supplied to the recording head 61 by way of the compressed contact member 59, the filter 60, and the ink supply tube 62, hence ink 53 in the second containing chamber 50 being consumed. After that, ink 53 in the second containing chamber 2 is continuously consumed until ink 53 in the second containing chamber 50 is completely used. After ink 53 in the second containing chamber 50 is no longer available, ink remaining in the negative pressure generating member 56 is consumed. When this ink is completely used, the ink tank becomes empty.
Now, FIG. 13 is a cross-sectional view which shows a second conventional example.
The structure of this conventional example is almost the same as that of the first conventional example shown in FIG. 12. However, the connecting unit (a rubber plug 70) of a recording head 73 is arranged on the lower part of the second containing chamber 50 which is not communicated with the air outside. This is difference between them. The recording head 73 and the second containing chamber 50 are coupled by the joint needle 71 of the recording head 73 which is pierced into the rubber plug 70 arranged on the bottom face of the second containing chamber 50.
Hereunder, with the reference to FIG. 13, the operation of this conventional example will be described.
When a printing apparatus begins its printing operation, the ink which has been absorbed into the negative pressure generating member 56 is consumed at first as in the first conventional example, and the height of the ink boundary face of the first containing chamber 51 is lowered. As ink consumption advances so that the height of the ink boundary face 57 of the first containing chamber 51 is made from a level at A to a level at B in FIG. 13 to reach the upper edge of the atmospheric induction groove 62, the air outside 55A is induced into the second containing chamber 50 as a bubble 54 through the atmospheric induction groove 62. When a bubble 54 enter the second containing chamber 50, the amount of air in the second containing chamber 50 becomes greater to press the ink boundary face 52 of the second containing chamber 50 downward.
Thus, the portion of ink 53 which has been pressed downward is allowed to flow directly into the recording head through the joint needle 71. Ink 53 in the second containing chamber 50 begins to be consumed. After that, ink 53 in the second containing chamber 50 is continuously consumed until ink 53 in the second containing chamber 50 is completely used. Even after ink 53 is no longer available in the second containing chamber 50, ink still remains in the negative pressure generating member 56. Here, however, the ink tank is considered to have been completely used up irrespective of such ink remainders in the ink tank.
Both ink tanks shown in FIG. 12 and FIG. 13 are excellent in the ink retaining efficiency.
Now, in accordance with the second conventional example shown in FIG. 13, the negative pressure in the second containing chamber 50 is lost and the pressure becomes positive after ink 53 in the second containing chamber 50 has been completely consumed. As a result, the remaining ink in the negative pressure generating member 56 is no longer used and remains as it is. Also, there is a problem that the ink which resides on the upper part of the filter 72 is subjected to leaking from the recording head 73.
Also, along with the increase of recording speed of an ink jet recording apparatus in recent years, there is a case where a large amount of ink is led out from an ink tank in a shorter period of time. However, In accordance with the first conventional example, the pressure loss in the negative pressure generating member 56 may sometimes increase along with the increase of ink flow rate. There is a fear, then, that it becomes difficult to continue the stable supply of ink.
Further, both for the first conventional example and second conventional example, the air is accumulated in the second containing chamber 50 when ink 53 in the second containing chamber 50 is consumed. Here, however, the air, the temperature, and the pressure are not necessarily constant all the time. These are always subjected to changes depending on seasons and localities. With environmental changes, such as temperature changes, pressure changes, the air in the second containing chamber 50 is caused to expand or contract. Then, ink in the second containing chamber 50 flows into the negative pressure generating member 56 in the first containing chamber 51 or returns therefrom each time such changes take place. With the repetition of such events, a problem may be encountered that the amount of ink retained in the negative pressure generating member 56 tends to be increased, and lastly, it overflows and leaks onto the recording head 73.
The present invention is designed in consideration of the problems that the conventional art has encountered as discussed above. It is an object of the invention to provide a highly reliable ink tank and a liquid discharge recording apparatus provided with such ink tank, which is capable of supplying ink stably even when the nozzle numbers are increased or driving frequency is increased for higher printing without ink leakage due to environmental changes, such as temperature changes, pressure changes.
With a view to solving the aforesaid problems, the ink tank of the present invention comprises a first containing chamber for containing a negative pressure generating member for retaining liquid, being provided with a atmospheric communication hole to make the negative pressure generating member to be communicative with the air outside; and a second containing chamber communicated with the first containing chamber, at the same time, retaining liquid directly. For this ink tank, a liquid supply port for supplying liquid to the outside is provided for the first containing chamber, and the second containing chamber.
For the present invention thus structure, the ink supply port for supplying ink to the outside is provided in a mode to communicate with both the first containing chamber and the second containing chamber. When ink (liquid) supply begins to the outside, such as to the recording head, ink is supplied in the same manner as the conventional art. The consumption of ink advances, and after the ink boundary face reaches the atmospheric induction groove, ink in the second containing chamber is consumed. When such ink is no longer available, ink remaining in the negative pressure generating member is consumed.
In this way, not only it becomes possible to continue stable consumption of ink in the second containing chamber, but there is no possibility that only ink in the negative pressure generating member is consumed, and ink in the second containing chamber is unused and left as it is as in the conventional art. Even after ink in the second containing chamber is no longer available, ink in the first containing chamber can be used up to the last.
Also, the ink supply port of the present invention is provided in a mode to be communicated both with the first and second containing chambers.
Also, the negative pressure generating member contained in the first containing chamber is arranged to supply ink to the outside through a filter. Also, a member for receiving negative pressure generating member is provided in a position becoming the upper part of the filter in order to receive the negative pressure generating member contained in the first containing chamber. In this manner, it becomes possible to avoid the deformation of filter, because the negative pressure generating member is locally in contact with the filter beginning with the opening portion of the member for receiving the negative pressure generating member.
Also, the ink supply port of the present invention is provided with a first ink supply port and a second ink supply port for the first containing chamber and second containing chamber, respectively. With this arrangement, it becomes possible to separate the ink tank from the recording head unit easily.
Also, for the second ink supply port of the present invention, a rubber plug is provided to enable a joint needle to pierce it for transferring ink, and the first ink supply port is provided with an opening face larger than the diameter of the joint needle.
Ink supply from the second containing chamber becomes better than ink supply from the first containing chamber where the negative pressure generating member is arranged, but if the opening area of the first ink supply port is made larger than the diameter of the joint needle that executes the ink supply from the second containing chamber as described above, it becomes possible to substantially equalize the ink supply from each of the containing chambers to the outside, such as to the recording head. As a result, ink can be supplied to the outside equally from each of the containing chambers.
Also, the printing apparatus of the present invention has an ink tank for use of ink jet printing installed therefor.
Further, the second containing chamber of the present invention comprises air escapement means for exhausting the air accumulated in the second containing chamber, and liquid supply means for supplying liquid to the second containing chamber.
Also, the air escapement means of the present invention is an exhaust tube communicated with an exhaust pump for exhausting the air accumulated in the second containing chamber, as well as with the second containing chamber.
Also, the air escapement means of the present invention is arranged on the upper part of the second containing chamber, and provided with first closing means for cutting off communication with the exhaust tube at any time other than when exhausting the air accumulated in the second containing chamber.
A method for using the aforesaid air escapement means and ink supply means may be structured in consideration of the following:
When the air is accumulated in the second containing chamber, the operation of the exhaust pump begins to exhaust the air in the second containing chamber. Then, ink is supplied from the ink supply tube to the second containing chamber. After that, when the air in the second containing chamber has been exhausted, the operation of the exhaust pump and the ink supply are suspended.
With these means used in this way, it becomes possible to suppress ink shift from the second containing chamber to the first containing chamber due to the expansion or contraction of the air accumulated in the second containing chamber, which may be caused by the environmental changes, such as temperature changes and pressure changes. Thus, ink leakage can be prevented. Also, when ink in the second containing chamber is no longer available, ink is supplied from the ink supply tube to the second containing chamber. As a result, there is no need for frequent replacement of ink tanks. Moreover, as the exhaust tube and ink supply tube are made separable from the second containing chamber, the structure of the apparatus can be made simpler to make the apparatus smaller at lower costs of manufacture.
Also, for the present invention, the exhaust tube is structured to be separable from the second containing chamber, and provided with second closing means for enhancing airtightness when the exhaust tube is communicated with the second containing chamber.
Also, for the present invention, the ink supply means comprises an ink supply tube for supplying ink to the second containing chamber, and a switching cock provided for the ink supply tube to supply or cut off ink to flow in the ink supply tube.
Also, for the present invention, the ink supply tube is made separable from the second containing chamber, and the ink supply tube is provided with an ink injection needle for connection with the second containing chamber, and the second containing chamber is provided with a rubber plug having a hole for the ink injection needle to be inserted.